title: Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(N-isopropylacrylamide) telechelics: synthesis and behavior of physical hydrogels.
abstract: Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS)-capped poly(N-isopropylacrylamide) (PNIPAAm) telechelics with variable lengths of PNIPAAm midblocks were synthesized by the combination of reversible addition-fragmentation chain transfer polymerization (RAFT) and the copper-catalyzed Huisgen 1,3-cycloaddition (i.e., click chemistry). The POSS-capped trithiocarbonate was synthesized and used as the chain transfer agent for the RAFT polymerization of N-isopropylacrylamide. The organic-inorganic amphiphilic telechelics were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). Atomic force microscopy (AFM) shows that all the POSS-capped PNIPAAm telechelics exhibited microphase-separated morphologies, in which the POSS terminal groups were self-assembled into the microdomains and dispersed into the continuous PNIPAAm matrices. The POSS nanodomains could behave as the physical cross-linking sites and as a result the physical hydrogels were formed while these POSS-capped PNIPAAm telechelics were subjected to the solubility tests with water. These physical hydrogels possessed well-defined volume phase transition phenomena and displayed rapid reswelling and deswelling thermoresponsive behavior compared to control PNIPAAm hydrogel.
authors.affiliation: Department of Polymer Science and Engineering and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Ke
authors.initials: K
authors.lastname: Zeng
authors.forename: Sixun
authors.initials: S
authors.lastname: Zheng
mesh_terms: D000042:Absorption; D000180:Acrylic Resins / Q000737:chemistry*; D006244:Hardness; D020100:Hydrogels / Q000737:chemistry*; D008422:Materials Testing
chemical_list: D000180:Acrylic Resins; D020100:Hydrogels; C052970:poly-N-isopropylacrylamide